Communication techniques using visible light have been proposed. For example, as in Patent Literatures (PTLs) 1 and 2, there are proposals on a video display apparatus including a display, a projector, etc., to superimpose visible light communication information on normal video to be displayed and then display resultant video.
In addition, there are the digital watermark technology applied to printed materials, and techniques of displaying QR codes (registered trademark), barcodes, etc., in images and using encoded signals thereof to spread information to the Internet world though imaging devices such as mobile phones, smart phones, and digital cameras.
However, since these are achieved by superimposition of encoded visible light communication signals as a part of control on a backlight while video signals are displayed by way of driving each pixel and controlling the backlight, these can be applied only to video display devices which display video by controlling the two systems.
Another devised method is, for example, superimposing information on an entire image inconspicuously in the form of watermark and decoding the superimposed information on a receiver side, that is, transmitting and receiving, in or without synchronization with video, relevant information, etc., that is information different from the video, using a video display apparatus. There has also been an, approach such as attempting to separate information quickly with use of an existing typical receiver although some deterioration is seen in video.